RE: Extract variable string from a based DS using a pointer

Have you looked at using a null terminated string? The %str() bif makes
them very easy to use and they can be any length between 1 and 65534
characters long. I don't know what your API is doing or what it is
written in, but to quote the RPG manual "%STR is used to create or use
null-terminated character strings, which are very
commonly used in C and C++ applications." so it might be a good fit for
your API. All it requires is a pointer pointing to a big enough area of
allocated memory.

Joe Lee

>>> davem@xxxxxxxx 12/16/2004 16:28:59 >>>
Thanks Bob,

This data structure is one of many that can be filled in by an API.  I

guess I didn't previously understand about no storage being allocated
when 
using BASED.

Let me rephrase your answer.

If I declare TextData as a 32K variable then assign a value to the
textPtr, 
as long as I don't excede the textLen (as returned by the API) when I 
reference TextData, I should be okay. Any TextData characters beyond
the 
TextLen specified can be anything in that happens to be in that area of

memory, but I do not have a full 32K field allocated.  Do I have this
right?

I thought about a VARYING field, but since this is a structure returned
by 
an API, I didn't think the variable field would be populated correctly
by 
the API (it would return data in the two length bytes).

At 03:40 PM 12/16/2004, you wrote:
>Are you trying to simulate a VARYING field? Looks like it to me.
>
>D TextDS    DS                       BASED(textPtr)
>D  TextLen                     5I 0
>D  TextData                32766A
>
>
>If you use BASED, no storage is allocated for TEXTDS, so it does not
matter
>if you declare TEXTDATA as a 32K variable. That way SUBST and other
>operation will work the way you want.
>
>If you want to NOT use this suggestion, and you simply want to copy
from
>that memory location, use this:
>
>   Eval     memcpy(%addr(target) : textPtr + 2: some-length-here )
>
>
>
>But why not just use a VARYING field?

Dave Murvin
DRM Enterprises, Inc.


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